JACKSONVILLE – The timing couldn't have been worse.

Not that there's a good time to be out for the remainder of a season, but Paul Posluszny said to get hurt now, with the Jaguars' defense starting to play as he and his teammates envisioned …

Well, it's just difficult. Really difficult.

"It's not easy," Posluszny said Monday, a day after he sustained a season-ending torn pectoral muscle in the Jaguars' 24-6 victory over the Cleveland Browns at EverBank Field.

"You get the feeling now that we're just starting to pick things up, and the team's going to roll a little bit and get on a nice winning streak and play some good ball. You want to be a part of that, so it's tough to get hurt now and know I'm not going to play football for a long time."

Posluszny, the Jaguars' starting middle linebacker and tackles leader each of the last three seasons, will be placed on injured reserve this week, the team announced on Monday. Veteran J.T. Thomas is expected to move to middle linebacker from the Otto position, where he has started the last four games.

"Poz does so much for us as a team in general," Thomas said. "He's a great leader and does so much for our room. All of the guys on our team look up to him for leadership. That's a tough loss for us."

Defensive tackle Sen'Derrick Marks called the loss of Posluszny "huge."

"Poz is our leader," Marks said. "We always say, 'The star of our defense is our defense,' but Poz is our leader. He's a guy who knows everything down to a 'T.' He keeps the defense gelled together. With Poz down, it will be a big loss for us, but it's the NFL. It's the Next-Man-Up Mentality. Our guys understand that."

Dekoda Watson and LaRoy Reynolds will compete for time at the Otto position, with Watson having been signed to play the position in the offseason and Reynolds starting the first three regular-season games there.

The Jaguars on Monday also announced that defensive end Andre Branch will miss about six weeks with a groin injury sustained against the Browns, meaning the Jaguars will be without two significant contributors to a defense that has improved significantly in recent weeks.

Branch has three sacks this season.

"It's bad for us, but it will be big for us with guys stepping up to get more experience, so I think we'll make it work," Marks said.

The Jaguars, after allowing 152 points in the first four games of the season, have held each of their last three opponents – Pittsburgh, Tennessee and Cleveland – under 20 points.

That's the first time that has happened since 2007.

"We really got back down to the fundamentals," Posluszny said. "We got off to a tough start and we were trying to do too much. We wanted to have success early on, we were trying to do too much and that got us out of whack a little bit.

"It took a couple of games of getting beat up pretty bad to realize, 'We have to calm down, stick to the basics, take care of our jobs, handle fundamentals … then collectively, we'll play great.' That's what we're starting to do now."

Posluszny sustained the pectoral injury on a fourth-quarter sack of Browns quarterback Brian Hoyer. Although he said he knew immediately the injury was "out of the ordinary," he returned and finished the series before leaving the game.

"I knew something was wrong, but not that wrong," he said. "You know how it is: we're winning, we're up and you want to finish the game."

Posluszny said he expects to have surgery this week, and said doctors have told him it won't affect preparation for next season.

"It's going to be difficult, because we love to play the game," Posluszny said. "It's going to be tough to sit and watch, but now it's going to be my job to do everything I can to help out the other linebackers get ready to play. It will be hard."

Also around the Jaguars Monday:

*The Jaguars activated rookie defensive end Chris Smith from the practice squad. Smith, a fifth-round selection from Arkansas, was on the 53-man roster in Week 1, but was inactive for that game. The Jaguars liked Smith's pass-rushing skills in the offseason, and he could work his way into a role in the team's lightning package in Branch's absence. "It's kind of bittersweet," Smith said. "You hate for somebody to go down. Branch is like a big brother to me. Since I got here, he's been teaching me moves and how to adjust to the league, so it hurts. Then again, you have to take advantage of your opportunity and help the team." …

*Thomas said one adjustment moving to the middle will be facilitating communication. Thomas and Posluszny had been the two Jaguars defenders with in-helmet communication devices, with Posluszny wearing it most of the time and Thomas wearing it when Posluszny wasn't in the game. Now, Thomas will receive communication from the sidelines as the middle linebacker. "I'm definitely looking forward to the opportunity," Thomas said. "Communication is key, whether it's me receiving a play in the headset or being able to communicate it to the rest of the defenders on the field." …

*Posluszny said if there is a "silver lining" to his injury it will be the chance to allow the knee that has hampered him much of the season to get necessary rest. He said he won't have surgery on the knee, but that time should heal the situation. "We've been fighting this for some time now," he said. "To find a positive, you'd say, 'Well, now we can let that heal up completely.'" …